Fix missing import in PHP-FPM's check

[DennisCGc]

What does this PR do?

This PR fixes the PHP-FPM status read out using FastCGI. sys is used in determining the default encoding when retrieving the data on FCGI_STDERR in Python 3. Failing to import it causes the plugin to crash.

Motivation

We'd like to collect metrics from & monitor our PHP-FPM instances using DataDog, but we don't want to expose those metrics using HTTP.

Additional Notes

There are no tests for handling the UNIX path case, but we configured our instances such that they are only accessible by a UNIX socket. I'm unsure as to how to add those tests. If you need tests, I'd like to give a try adding them.

I've also searched the issue list before creating this PR, and it seems #11480 was already created but closed, due to the fact that the bug report was incomplete.

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• PR title must be written as a CHANGELOG entry (see why)
• Files changes must correspond to the primary purpose of the PR as described in the title (small unrelated changes should have their own PR)
• PR must have changelog/ and integration/ labels attached

[codecov]

Codecov Report

Merging #12365 (21e6b88) into master (4d92271) will increase coverage by 0.00%.
The diff coverage is n/a.

Flag	Coverage Δ
php_fpm	90.25% <ø> (+0.84%)	⬆️

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[steveny91]

Thanks for catching that!